Volume 18, Issue 46 (No.3&4-صفحات انگلیسی از 187 تا 191(چکیده) 2008)                   2008, 18(46): 768-784 | Back to browse issues page

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Investigation the Primary and Secondary Textures of Granitoidic Masses from North of the Golpayegan and their Emplacement Age Based on Field Surveys and Paleontological studies. Quarterly Journal of Science Kharazmi University. 2008; 18 (46) :768-784
URL: http://jsci.khu.ac.ir/article-1-1198-en.html
Abstract:   (5050 Views)
The granitoidic masses from northeast of the Golpayegan area were intruded in a metamorphic complex of Barrovian type and the some area caused contact metamorphism in the adjacent rocks. These masses in the QAP triangular diagram consist of tonalite, granodiorite, granite, alkali feldspar granite, monzogranite, quartz diorite, quartz monzonite and quartz monzodiorite. The aplitic and pegmatitic dykes can also be observed on the rim of these masses. The textures of granitoids are mainly based on primary textures [1)granitic texture, 2)poikilitic texture, 3)granophyric texture] and secondary textures[1)perthitic intergrowths, 2)myrmekite, 3)chloritization 4)sericitiza-tion, 5)kaolinitization]. Fabric and mineralogical study of granitoids show that the presence of k-feldspar mega crystals and rounded zircons could probably indicate the characteristics of S-type granitoids or granitoids with crustal origin. But presence of granophyric texture in some of tonalites shows that these masses are plagiogranite type which is considered as I-type granitoids or the granitoids with mantle origin. Presence of mylonitic texture in some other granitoids which have outcrops in the northeast Golpayegan (north of Varzaneh and Sfajerd villages) show that these masses were formed during an orogenic phase (Laramid). Based on studies conducted on conodont fossils obtained from crystallized calc schists and acrytarge in slates of the area which are introduced for the first time in Sanandaj-Sirjan Zone, the age of the metamorphic rocks, that previously were documented as Precambrian, was reviewed and show that they belongs to Paleozoic. Thus, the age of granitoids from the north of Golpayegan was considered younger than late Jurassic and older than Oligocene. In this paper, based on field observations and paleontological studies, the age of granitoids from the north of Golpayegan emplacement were documented for the first time. Thus, throgh studing the texture and age of the granitoidic masses from the Golpayegan area, it could be concluded that some of these masses (granophyric granitoids or I-type) were formed during Jurassic and initial Cretaceous and synchronous with subduction and before continental collision, and some other masses (mylonitic granitoids) were formed during continental collision and synchronous with the end of deformations at the end of orogenic events. Some others (often S-type granitoids), finally, were formed in late Cretaceous-Paleocene after collision of the Arabian plate with the Iranian plate at the end of Cretaceous.
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Published: 2008/04/15

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